I hadn't noticed that their ads service was done via Google. That's worrying alright.
It's still a better bet than using Google directly. The ixquick folks talk a lot about privacy, so maybe they've figured a way to do this right. For example, if they didn't send an IP address to Google, and just sent streams of keywords without any you-specific identifier (or with an ixquick identifier which ixquick ties to your IP address but which is meaningless to Google), then there'd be no problem. If.